Small vesicles could serve as delivery vehicles for proteins, RNA/DNA and other drug substances.

Exosomes, which are lipid vesicles, were once thought to only remove waste products from cells. However, since Swedish researcher Jan Lötvall at the University of Gothenburg demonstrated that exosomes also transport proteins and genetic information, including messenger RNA to make proteins and microRNAs to regulate the expression of genes between cells, they have become the subject of intense interest.

Vesicles have been shown to play a role in the spread of cancer, metabolic conditions such as diabetes and obesity, and other diseases. They may also be involved in the distribution of distributing amyloid-β, the plaque-forming protein that accumulates in the brains of people with Alzheimer’s disease. 

Several companies are working to use exosomes to deliver drugs to parts of the body that are typically difficult to reach. All cells make and take up exosomes, so they have potential application in just about every diseases. These efforts are targeting all types of drug substances, including small molecules, RNA therapies and proteins. Others include the use of exosomes in viral gene therapy and as delivery vesicles for CRISPR gene-editing tools. For instance, exosomes may provide a non-toxic alternative to synthetic lipid nanoparticles for the delivery of siRNA and other RNA therapies to cells in a multitude of organs, rather than building up in the liver

Others are focused on developing exosomes derived from stem cells as therapies, some of which could enter into clinical trials as soon as 2019. Diagnostics for cancer based on exosomes are already on the market.

One of the challenges researchers face is the wide diversity of vesicles produced from a single cell line, as well as the difficulty in separating them. Originally only two types were thought to exist – exosomes and microvesicles, but in actuality, there are many more. Producing consistent exosomes of the same size with the same quantity of loaded drug is crucial to the development of successful therapies.